The present invention generally relates to communication in a time division duplexing (TDD) system. More specifically, the present invention relates to providing a method and system for managing change-over in radio functionality, such as transmit-to-receive or receive-to-transmit, at a radio front-end in a TDD system.
In TDD systems, it is required to switch between transmit (TX) and receive (RX) functionalities in a radio portion of the TDD systems. This switching between TX and RX needs to occur at relative precise time instances. In addition to the switching, it is often necessary to send control information to a Radio frequency Integrated Circuit (RF IC) in order to adapt its functionality to conditions that evolve over time.
Further, a radio front-end of a communication device in a TDD system may have to switch back and forth between RX and TX functionalities. For this purpose, conventionally, the control information is sent to the radio front-end using a plurality of control commands. The control commands need to be applied at different time stamps to reflect the constraints or desired results, based on several finite physical quantities. The finite physical quantities may comprise a settling time of a filter, a time constant associated with a bias circuitry in a power amplifier of a transmitter, etc.
Moreover, in conventional TDD systems, the control commands are transmitted from a baseband processing integrated circuit (IC) to a RF IC over a serial interface. In addition to the serial interface, there can be additional signals, General Purpose Input/Output (GPIO) signals that connect the RF ICs and baseband ICs. In such a system, the control commands are transferred over the serial interface and subsequent to the control commands, the GPIO signals are used to affect the previously transferred control commands. Such serial interfaces may require one or more GPIO signals between the RF ICs and baseband ICs. These additional GPIO pins add additional size and cost to the system. Also, the additional GPIO signals impose an overhead on the system thereby decreasing throughput of the system.
Further, in some conventional applications, a microprocessor is used to control the serial interface. In these applications the control commands in the RF IC have an immediate effect. Specifically, when the control commands need to be sent, the microprocessor is interrupted with a high priority low latency interrupt. The control commands are sent by the microprocessor and they have an immediate effect in the RF IC. Specifically, the microprocessor stops the running tasks and sends the control commands at the precise time, and then it goes back to the tasks it was performing before being interrupted. The high priority low latency interrupts place real-time constraints on the microprocessor. Additionally, the microprocessor takes some time to respond to the interrupt. Therefore, it is necessary to interrupt the microprocessor slightly in advance. However, the time the microprocessor takes to respond to the interrupt is variable; therefore, the timing of control commands may be less accurate than desired. Moreover, the requirement of accurate timing places a significant constraint on the control software.
Furthermore, in some communication systems, a real time operating system (RTOS) is used, for instance, to control many aspects of the communication system, to enable a plurality of tasks to run in parallel, to allow communication between tasks, and to provide other useful software functions. However, some RTOSs suffer from a significant latency and variability, which are associated with an interrupt. This latency and variability may be reduced, but often at the expense of system performance.
Therefore, there is a need for a method and system that allows control information to be applied in RF ICs at a precise time, without the overhead of additional signals being placed on the software.